Study links outdoor nighttime light to increased myopia risk in Hong Kong children

A large, population-based study of Hong Kong schoolchildren has found that exposure to outdoor artificial light at night (ALAN) is associated with a higher risk of developing myopia, according to research using satellite-derived lighting data collected over a multi-year period.¹

“Outdoor ALAN has emerged as a significant source of environmental pollution. However, epidemiological evidence on its impact on childhood myopia development remains limited,” the study authors, led by first author Yingan Li of the Department of Ophthalmology and Visual Sciences, Faculty of Medicine at The Chinese University of Hong Kong in the Hong Kong Special Administrative Region of China, stated.

The study

Researchers drew on data from the Hong Kong Children Eye Study (HKCES), an ongoing cohort study of schoolchildren established in 2015. From an initial pool of 24,502 children, researchers included 19,114 participants in a cross-sectional analysis and 2558 myopia-free children in a three-year prospective cohort analysis, following STROBE reporting guidelines. The study was approved by the Joint Chinese University of Hong Kong–New Territories East Cluster Clinical Research Ethics Committee.¹

Outdoor ALAN exposure was measured using nighttime light data from the Earth Observation Group, based on satellite readings from the VIIRS/DNB sensor, calculated within a 500-meter buffer around each child's residence. Myopia was defined as a spherical equivalent refraction of −0.50 diopters or less in either eye, measured via cycloplegic autorefraction.¹

Key findings

At baseline, 27.0% of the 19,114 children had myopia. In the maximally adjusted statistical model, each interquartile range increase in outdoor ALAN exposure was associated with an 8% higher prevalence of myopia (odds ratio, 1.08; 95% CI, 1.02–1.15).¹

Among the 2558 children followed prospectively, 55.1% developed myopia over 3 years. In this group, each interquartile range increase in ALAN exposure was associated with a 26% higher risk of developing myopia (hazard ratio, 1.26; 95% CI, 1.16–1.37). Children in the highest exposure quartile had a 1.34-fold higher risk of developing myopia compared with those in the lowest quartile.¹

The relationship between ALAN exposure and myopia was non-linear. For myopia incidence, risk remained relatively stable at lower exposure levels but rose sharply above a threshold of approximately 93.08 nW/cm²/sr.¹

Subgroup findings

The association between ALAN and incident myopia was significantly more pronounced in older children (age 7.35 years and above) compared with younger children. Subgroup analyses also indicated stronger associations among children with both parents having myopia and those from lower-income households, though these differences did not reach statistical significance as effect modifiers.¹

“Comparison with those lost to follow-up showed that included participants had higher rates of parental myopia and higher parents’ educational levels, despite a higher proportion being from lower income families. However, absolute differences in behavioral factors were minimal,” the study authors stated.

Context and limitations

The study's authors note this is among the first longitudinal cohort studies to examine outdoor ALAN and incident myopia, building on a prior cross-sectional study by Liu et al (2024) that found a similar association in Chinese adolescents using school-address data.¹

The authors acknowledge several limitations, including reliance on satellite data as a proxy for individual light exposure, the absence of data on indoor light-blocking measures such as curtains, loss to follow-up in the prospective cohort, and the predominantly Hong Kong Chinese study population, which may limit generalizability to other groups.¹

Conclusion

The study's authors state that findings should be interpreted cautiously given its observational design and describe a need for further research incorporating objective individual light monitoring and experimental studies to confirm the results and clarify underlying biological mechanisms.¹

“Given that outdoor ALAN is emerging as a pervasive environmental hazard for refractive development, future efforts to curb the myopia epidemic may benefit from considering the integration of current strategies with broader public health and urban planning guidelines to mitigate excessive outdoor ALAN levels,” the study authors stated.

Reference:

1. Li Y, Zhang Y, Kam KW, et al. Outdoor artificial light at night exposure and risk of myopia: A cross-sectional and prospective cohort study among Hong Kong children. 2026;303:124647. https://doi.org/10.1016/j.envres.2026.124647